Making a success of a virtualisation strategy is mainly about getting the planning right, according to Capita, which uses VMware's virtualisation software.

But the professional services company argues it is also important to set out with realistic ambitions and be prepared for trouble from Windows teams who may not be as enthusiastic as Unix teams about products such as VMware's software.

Capita's senior IT infrastructure manager, Shaymus Kennedy, told delegates at the London-based VMware user conference on Tuesday: "Rolling out VMware is 80 percent planning and 20 percent execution. If you don't get the planning right, you will have difficulties."

Kennedy was clear about the benefits to be gained from virtualisation, stressing that it reduced costs, simplified administration and offered much more flexible IT environments. However, he said that it would be wrong to expect quick returns with little effort. "I cannot stress too much the importance of preparation," he said. "It is absolutely vital, and you must get buy-in. People have to be able to see and understand the benefits and what it takes to get there."

Capita has been using VMware for three years in Ireland and, in that time, Kennedy believes, the company has come a long way. "VMware has had challenges around support," he told ZDNet.co.uk. "At times we have not got the support we want. But we believe it is coming right now." It was important to remember that "VMware does not solve everything", he said.

A big challenge was that, by installing VMware software, the company had to buy extra licences, which represented a high initial cost. "You cannot necessarily consolidate your licences and save a lot of money," Kennedy said. For that reason, having a "really good" cost-of-ownership model in place is very important.

"If you look at your investment over three or four years and you have a good cost-of-ownership model, then you will find the cost will justify itself", Kennedy added. "If you are just looking at the short tem, then I can understand why the costs will appear to be quite high."

Capita has about 10,000 employees in Ireland, with 27 percent of users working in virtualised environments.